The present invention relates generally to bolt locating devices and pertains particularly to a new and improved apparatus for the location and accurate drilling of bolt holes for stud plates for slab constructed buildings.
Many residential and commercial buildings are constructed by what is commonly known as slab and frame construction. A concrete slab is typically poured on site, and leveled for forming the floor and foundation for the building. A wood frame structure is then placed on and secured to the slab.
When the slab is being poured, bolts or studs are placed in the concrete, extending upward along rows where plates for the framing is to be secured to the slab floor. Once the concrete has dried, the framer, in order to attach the plate to the floor, typically places the plate member, which is a two-by-six or two-by-four depending on the construction, directly on top of the preset bolts and hits the plate with a hammer over each bolt to mark the position of the bolt. Holes are then drilled where the depressions are made, and the plate then fitted over the bolts to the slab.
One difficulty with this approach is that the plate may not be as precisely aligned as is desired with the edge of the slab. Another difficulty is that the bolts are frequently never quite perpendicular, and the resulting hole is therefore not properly aligned. Another difficulty is that the bolts are frequently of a different height, such that only certain holes are marked. These problems of misalignment are time consuming and frustrating for the carpenter to correct or accommodate.
One solution to this problem is proposed in U.S. Pat. No. 3,406,460 issued Oct. 22, 1968 to Colwell and entitled "Bolt Hole Marker". This device comprises a measuring arm 16 having an end 18 for engagement with the bolt, and a marking punch 24 having a head 26, and a point 20 mounted within the arm at a distance equaling the width of the plate. In use, the plate is aligned adjacent to the bolts, and the marker is utilized to locate the lateral position of the hole, and is tapped with a hammer to make an indentation where the hole is to be placed. Again, this provides one difficulty in that the carpenter may not precisely align the markers square to the bolt, resulting in longitudinal mis-positioning of the bolt sufficient to make mounting of the plate difficult. Another problem is that in drilling the holes, the drill may not be precisely centered within the punch mark, thereby resulting in the hole being slightly out of position. This again results in difficulty in mounting the plate once the holes have been drilled.
In my aforementioned application, I disclosed an improved bolt hole locating and drilling device of simple construction. I have subsequently devised an apparatus for more precisely and effectively locating and drilling the holes.